Climate of Chiang Mai

The weather you can expect when visiting Chiang Mai depends of course on the season. Chiang Mai’s climate can be roughly divided in three seasons, the rainy season, the dry and cool season, and the dry and warm season. Knowing these seasons will help you decide when are the best months to visit Chiang Mai.

First let's have a look at monthly temperature and rainfall. The following table shows high, mean, and low temperatures for each month in degrees Celcius (°C).

Temperature

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

High

28.9

32.2

34.9

36.1

34.1

32.3

31.7

31.1

31.3

31.1

29.8

28.3

Mean

20.5

22.9

26.4

28.7

28.1

27.3

27.0

26.6

26.5

25.8

23.8

21.0

Low

13.7

14.9

18.2

21.8

23.4

23.7

23.6

23.4

23.0

21.8

19.0

15.0

Over an entire year the average high temperature is 31.8 °C, the average mean temperature is 25.4 °C and the average low temperature is 20.1 °C

The next table shows the monthly precipitation, which generally means rain although an occasional hail storm may occur.

Precipitation

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Mean (mm)

7

5

13

50

158

132

161

236

228

122

53

20

On average that is about 99 millimeter per month, but averages like this are not very useful. More important is to know that of the total 1185 mm of rain, about 87% falls between May and October.

Based on the above tables, the temperature and rainfall graphs for Chiang Mai look like this:

Chiang Mai temperature

Chiang Mai precipitation

Some average climate data for Chiang Mai

Let's summarize Chiang Mai's climate by looking at some averages and some extremes:

Temperature

Average temperature throughout the year

25.4 °C

High temperatures (daytime)

Average high temperature

31.8 °C

Highest monthly mean high temperature
(April)

36.1 °C

Lowest monthly mean high temperature
(January)

28.9 °C

Low temperatures (night)

Average low temperature

20.1 °C

Highest monthly mean low temperature
(June)

23.7 °C

Lowest monthly mean low (January)

13.7 °C

Days with frost

0 days

Temperature range

Average temperature range (day-night)

11.5 °C

Highest temperature range (January)

15.2 °C

Lowest temperature range (August)

7.7 °C

Rainfall

Total yearly rainfall

1185 mm

Average monthly rainfall

99 mm

Days with more than 0.1 mm rain

109

Driest month (January)

7 mm

Rainy days in driest month

± 1 day

Wettest month (August)

236 mm

Rainy days in wettest month

± 18 days

Seasons in Chiang Mai

Chiang Mai has six wet months (May-October) which can be called the rainy season. During these wet months the weather is relatively warm and air humidity is high (30-65%). This wet weather is caused by the south-west monsoon, which usually arrives from India during the month of May. Most rain can be expected during August and September.

Expect sunshine on a cloudy day

The other six months (the north-east monsoon) may be called the dry season, but within this dry season you can distinguish a cooler period (November-February) and a warmer period (March-May). Throughout the dry seasons the air humidity is relatively low (5-25%).

Compared to the central and southern parts of Thailand, Chiang Mai is slightly cooler and enjoys a lower relatively humidity. It is especially this lower humidity which contributes to the nice climate in Chiang Mai.

Note that especially during December and January, which you could call the Chiang Mai winter, the evenings are very cool and you will need some warm clothes during this period. A sweater or jacket will be needed after sunset, but during daytime you can walk around in shorts and t-shirts.

When to visit Chiang Mai

If you enjoy a rainy holiday, just come in August or September and you will get what you deserve. Most people however will opt for the Chiang Mai winter season and enjoy the dry and slightly cooler weather. The best months to visit are probably from October to February.

Waterfalls are good at the end of the rainy season

During October-November you still may get some rain, but the advantage is that so soon after the rainy season everything is still green and clean and the many waterfalls near Chiang Mai are still with a lot of water. December and January have excellent weather, warm during the day and cool during the evening and night. You will need a sweater or jacket after sunset. Towards the end of February and in March temperatures are going up, and as it has not rained for several months the environment gets rather dry and sometimes dusty.

Especially during the month of March, Chiang Mai often suffers from air pollution caused by forest and bush fires, but also because farmers tend to burn their old rice fields in preparation for the new season. All these fires cause a lot of smoke and dust, which probably make March the worst month to visit Chiang Mai.

Air pollution because of slash and burn cultivation.

April is also still dry and usually quite hot, but a visit during the middle of April is worthwhile as you can enjoy the yearly Songkran festival, which celebrates the Thai New Year. The monsoon rains usually start in May, reaching their peak during August and September.

April is warm in Chiang Mai, but you can cool down during the Songkran festival.

Note: The above climate data for Chiang Mai were compiled from a number of sources. Each source gives slightly different figures. Differences depend on the exact location of where the data were collected, and also the period over which the average was calculated. Climate Change is of course another contributing factor. Don't quote the above data but just use them to get an idea of the climate in Chiang Mai. Weather will change from year to year anyway.

Nice charts & graphs of rainfall, humidity, and temperature in Chiang Mai. But where is Chiang Mai? Are you measuring the city of Chiang Mai within the moat, greater Chiang Mai, or Chiang Mai Province which includes the cold mountainous regions?

I have been going to Chiang Mai for the last 14 years around Nov. and Dec. Rain around this time is a novelty. Yes there is some welcome rain occasionally and some may even be heavy but within the hour you may see just a few paddles. One thing though you should leave Chiang Mai around the 15th Feb. because that is the time when the farmers start burning their rice fields to make them ready for a new crop. Otherwise this season, Nov.-Feb. for us snowbirds to visit Chiang Mai and the surrounding will be a pleasant experience. May be we meet at the night market or while you visit an elephant camp.
Globetrotter